Coat 8x8" baking pan with nonstick vegetable oil spray; line with parchment, leaving overhang on all sides. Toast 1 1/2 cups cashews, 6 tablespoons raw sesame seeds, and 5 tablespoons flaxseed in separate areas on a rimmed baking sheet in a 350° oven, stirring occasionally (but not mixing), until golden brown, 10–12 minutes. Let cool. Set aside 2 tablespoons sesame seeds and 1 tablespoon flaxseed.
Process cashews and remaining seeds with 1/4 cup wheat bran, 3/4 teaspoon kosher salt, and 1/4 teaspoon ground cardamom in a food processor until mostly finely chopped. Place in a medium bowl. Bring 1/2 cup pure maple syrup and 1 tablespoon coconut oil to a boil in a small saucepan; cook, stirring, 1 minute. Pour over cashew mixture and stir to coat. Press mixture firmly into prepared pan with wet hands (it will be sticky). Top with reserved seeds; press to adhere. Bake until golden brown, 25–30 minutes. Let cool, then cut into bars.